Connectionally known in the image formation of a color printing system is a system for performing processing for each kind of drawing object by effecting a switching of color processing parameters of color-conversion color lock-up tables (hereinafter referred to as color conversion tables) and halftone cells on a threshold table used at the tone processing time. An expanded type of system is also proposed which, when a drawing object is an image, decides the kind of image with a command in a page description language (PDL) and, by doing so, performs processing by effecting a switching of color processing parameters.
As the examples of the prior art, there are Jpn. Pat. Appln. KOKAI Publication Nos. 2001-69360 and 2000-331147 and these disclose the technique for deciding the attribute of the drawing object in the color image processing method and performing color processing based on the result of decision.
When a human looks at an object, what is called a color “area” effect works. The color “area” effect means an effect by which the lightness and saturation of an object look different due to its color-drawn area. In the above-mentioned prior art technique, color correction while giving consideration to such a color “area” effect is not made and it is, therefore, not possible to obtain any adequate printing result. Thus a problem is involved. Even in the switching of halftone cells, such a switching is not effected in a way to give consideration to the relation of the halftones between the adjacent objects and, depending upon a combination of such halftones, there is a problem with which a printed thing looks unnatural sometimes.
Further, the kind of image is not specified in a way to make adequate use of image information to be printed and color conversion and tone correction are not made in a way to be matched to the kind of image. And any adequate color correction is not effected in a way to be matched to the kind of image, so that a problem is involved.